package com.op.teachingliteapp.util.http.override;

import com.android.volley.Cache;
import com.android.volley.NetworkResponse;

import org.apache.http.impl.cookie.DateParseException;
import org.apache.http.impl.cookie.DateUtils;
import org.apache.http.protocol.HTTP;

import java.util.Map;

/**
 * Created by Michael on 2015/08/29.
 */
public class HttpHeaderParser {

    /**
     * Extracts a {@link Cache.Entry} from a {@link NetworkResponse}.
     * Cache-control headers are ignored. SoftTtl == 3 mins, ttl == 24 hours.
     *
     * @param response The network response to parse headers from
     * @return a cache entry for the given response, or null if the response is not cacheable.
     */
    public static Cache.Entry parseIgnoreCacheHeaders(NetworkResponse response) {
        long now = System.currentTimeMillis();

        Map<String, String> headers = response.headers;
        long serverDate = 0;
        String serverEtag = null;
        String headerValue;

        headerValue = headers.get("Date");
        if (headerValue != null) {
            serverDate = HttpHeaderParser.parseDateAsEpoch(headerValue);
        }

        serverEtag = headers.get("ETag");

        final long cacheHitButRefreshed = 3 * 60 * 1000; // in 3 minutes cache will be hit, but also refreshed on background
        final long cacheExpired = 24 * 60 * 60 * 1000; // in 24 hours this cache entry expires completely
        final long softExpire = now + cacheHitButRefreshed;
        final long ttl = now + cacheExpired;

        Cache.Entry entry = new Cache.Entry();
        entry.data = response.data;
        entry.etag = serverEtag;
        entry.softTtl = softExpire;
        entry.ttl = ttl;
        entry.serverDate = serverDate;
        entry.responseHeaders = headers;

        return entry;
    }

    /**
     * Parse date in RFC1123 format, and return its value as epoch
     */
    public static long parseDateAsEpoch(String dateStr) {
        try {
            // Parse date in RFC1123 format if this header contains one
            return DateUtils.parseDate(dateStr).getTime();
        } catch (DateParseException e) {
            // Date in invalid format, fallback to 0
            return 0;
        }
    }

    /**
     * Retrieve a charset from headers
     *
     * @param headers An {@link java.util.Map} of headers
     * @param defaultCharset Charset to return if none can be found
     * @return Returns the charset specified in the Content-Type of this header,
     * or the defaultCharset if none can be found.
     */
    public static String parseCharset(Map<String, String> headers, String defaultCharset) {
        String contentType = headers.get(HTTP.CONTENT_TYPE);
        if (contentType != null) {
            String[] params = contentType.split(";");
            for (int i = 1; i < params.length; i++) {
                String[] pair = params[i].trim().split("=");
                if (pair.length == 2) {
                    if (pair[0].equals("charset")) {
                        return pair[1];
                    }
                }
            }
        }

        return defaultCharset;
    }

    /**
     * Returns the charset specified in the Content-Type of this header,
     * or the HTTP default (ISO-8859-1) if none can be found.
     */
    public static String parseCharset(Map<String, String> headers) {
        return parseCharset(headers, HTTP.DEFAULT_CONTENT_CHARSET);
    }
}
